The long-term objective of this project is to identify the mechanism of time perception and timed behavior. The proposed studies will concern the characteristics of the internal clock and the nature of the memory representation of durations of time. (1) The first aim is to determine whether oscillatory processes are involved in timing stimuli in the second-to-minute range, and to explore the characteristics of these oscillatory processes. Rats will be tested in lever boxes and activity boxes under conditions of food being available at predictably spaced intervals (fixed intervals, or fixed intervals plus a small change) to examine systematic discrepancies from beginning to respond at a constant proportion of the interval (the oscillator signature), and to examine the effects of occasional perturbations of the intervals (the phase-response curve). Other experiments will provide food at unpredictable times (random intervals) to examine the determinants of the periodic behavior that emerge and the extent to which each of them can be entrained or selected. (2) The second aim is to determine whether memory for time is represented as a matrix of values. Rats will be tested with multiple time criteria (either simultaneously or successively) and the magnitude and direction of mutual influence will be used to determine the mutual influence of the memory of one time interval on the memory for another. (3) The third aim is to further develop a multiple-oscillator, connectionist model of timing that will fit the data quantitatively. The perception of time is a fundamental attribute of all mental processing, and various distortions of time perception is characteristic of various psychiatric disorders. In the short term, the most likely application of this research is in the development of some simple noninvasive neuropsychiatric tests of time perception that will serve as an aid for early diagnosis for several psychiatric disorders. In the long term, the value may be to increase understanding of the biological basis of several psychiatric disorders as they are manifested by distortions in time perception.